FIG. 1 shows a schematic configuration of a cigarette manufacturing apparatus. This cigarette manufacturing apparatus continuously supplies tobacco shreds 2a fed into a hopper 1 to a wrapping unit 4 by sucking them to the lower surface of a conveyor belt (tobacco band) provided in a suction unit 3. The suction amount (supply amount) of tobacco shreds 2a sucked to the lower surface of the conveyor belt 3a is controlled by a trimming disk 5. The wrapping unit 4 continuously wraps the tobacco shreds with an elongated cigarette paper 6 supplied continuously from a roll R to form a long tobacco rod 2b. This tobacco rod 2b is cut to predetermined lengths in a cutting section 7. For example, the tobacco rod 2b is cut into cigarette rods 2c of a double unit length, which corresponds to a length of substantially two final cigarettes, and the cigarette rods 2c are supplied to a filter attachment unit 8.
The wrapping unit 4 is provided with a garniture tape 4b drivingly run by a main shaft 4a. As shown in FIG. 2, the garniture tape 4b rolls both sides of the cigarette paper 6 inside and upward while conveying the cigarette paper 6 supplied from the roll R, and continuously wraps the tobacco shreds 2a supplied onto the cigarette paper 6 in cooperation with a tongue 4c disposed opposingly above the garniture tape 4b. By this wrapping operation, the long tobacco rod 2b, in which the tobacco shreds 2a are wrapped with the cigarette paper 6, is continuously formed. The running speed of the conveyor belt 3a, which determines the supply speed of tobacco shreds 2a to the wrapping unit 4, is determined in synchronization with the rotation of the main shaft 4a, that is, depending on the running speed of the garniture tape 4b.
The trimming disk 5 is rotated in synchronization with the rotation of the main shaft 4a (running speed of the garniture tape 4b). The trimming disk 5 regulates the thickness of tobacco shreds 2 sucked to the lower surface of the conveyor belt 3a, and controls the suction amount (supply amount) of tobacco shreds 2a conveyed to the wrapping unit 4 by scraping away the excess shreds. By the control of the supply amount of tobacco shreds 2a using the trimming disk 5, the amount of tobacco shreds 2a wrapped with the cigarette paper 6, that is, the amount (filling amount) of tobacco shreds 2a in the tobacco rod 2b is controlled.
The trimming disk 5 is provided with pockets 5a for partially increasing the filling amount of tobacco shreds 2a in the tobacco rod 2b. The presence of these pockets partially increases the suction amount (supply amount) of tobacco shreds 2a conveyed to the wrapping unit 4, for example, each time the disk makes a half turn. As a result, the filling amount (filling density) of tobacco shreds 2a in the tobacco rod 2b is increased partially at every predetermined portion in the lengthwise direction. The hardened portion where the filling density of tobacco shreds 2a is increased is the cut portion where the aforesaid cigarette rods 2c are cut off, and further each cigarette is cut off. As a result, the tobacco shreds 2 are prevented from dropping off the cigarette dense end.
The filling density of tobacco shreds 2a in the tobacco rod 2b is detected continuously by using, for example, a radiation density detector. By integrating the filling density of tobacco shreds 2a, which is continuously detected at every portion in the lengthwise direction of tobacco rod 2b in sequence, over a predetermined length in the lengthwise direction of tobacco rod 2b, for example, the total filling amount and average filling amount, and further the standard deviation of filling amount, and the like per one cigarette are determined.
In accordance with this detection result, the supply amount of tobacco shreds 2a is variably controlled, for example, by the trimming disk 5, so that the filling amount (filling density) of tobacco shreds 2a in the tobacco rod 2b is controlled. If it is judged from the aforementioned detection result that the total filling amount or average filling amount of tobacco shreds 2a per one cigarette is short, the cigarette rod 2c or cigarette cut from the tobacco rod 2b, which includes the portion where the filling amount is short, is rejected.
The tobacco shreds 2a sometimes drop off the cigarette dense end due to the deficiency of filling amount (filling density) of tobacco shreds 2a. Therefore, the state of the cigarette dense end is checked by using, for example, a photosensor or capacitance proximity sensor. If the dropping-off of tobacco shreds 2a is found, that cigarette (cigarette rod 2c) is also rejected.
As described above, even if the whole filling amount of tobacco shreds 2a in the tobacco rod 2b is controlled, some variations in filling density are naturally caused. In particular, as the cigarette manufacturing speed, specifically the wrapping speed of tobacco rod 2b, increases, the variations in the filling density in the lengthwise direction of tobacco rod 2b increases. For example, due to the slip of the cigarette paper 6 with respect to the garniture tape 4b, or the reaction of the tobacco shreds 2a when the tobacco shreds 2a are sucked to the conveyor belt (tobacco band), the filling density of tobacco shreds 2a in the tobacco rod 2b is increased (hard spot) or decreased (soft spot) locally.
The excess filling portion (hard spot) of tobacco shreds 2a hinders the air flow in the cigarette, exerting an influence upon the cigarette quality. Meanwhile, the deficient filling portion (soft spot) of tobacco shreds 2a causes variations in the burning state, for example, during smoking. Further, the deficient filling portion (soft spot) of tobacco shreds 2a hinders uniform smoking, and has an influence upon the change in burning velocity, the yielding amount of tar and nicotine, and in turn the smoking taste.
Conventionally, however, the filling state of tobacco shreds 2a in the tobacco rod 2b is monitored merely, for example, as the average filling amount etc. per one cigarette, as described above. Also, the dropping-off state of tobacco shreds 2a at the cut end of a cigarette is merely monitored.
The present invention was made in view of the above situation, and accordingly an object thereof is to detect a local excess filling portion (hard spot) and deficient filling portion (soft spot) of tobacco shreds in a tobacco rod efficiently and reliably, and to surely reject a cigarette rod or cigarette cut from the tobacco rod, which includes the local excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds.
Another object of the present invention is to improve the production quality of a cigarette by reliably rejecting a cigarette including the local excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds in consideration of the fact that these defective portions are liable to be produced as the cigarette manufacturing speed increases.
The present invention provides a cigarette manufacturing apparatus capable of achieving these objects.